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How Twitter Is Moving To the Cassandra Database
MyNoSQL has up an interview with Ryan King on how Twitter is transitioning to the Cassandra database. Here's some detailed background on Cassandra, which aims to "bring together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model." Before settling on Cassandra, the Twitter team looked into: "...HBase, Voldemort, MongoDB, MemcacheDB, Redis, Cassandra, HyperTable, and probably some others I'm forgetting. ... We're currently moving our largest (and most painful to maintain) table — the statuses table, which contains all tweets and retweets. ... Some side notes here about importing. We were originally trying to use the BinaryMemtable interface, but we actually found it to be too fast — it would saturate the backplane of our network. We've switched back to using the Thrift interface for bulk loading (and we still have to throttle it). The whole process takes about a week now. With infinite network bandwidth we could do it in about 7 hours on our current cluster." Relatedly, an anonymous reader notes that the upcoming NoSQL Live conference, which will take place in Boston March 11th, has announced their lineup of speakers and panelists including Ryan King and folks from LinkedIn, StumbleUpon, and Rackspace.
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First time I have ever heard anyone say that a database was too fast. Maybe there are network problems that also need to be addressed.
Scaling. If something turns out to be robust and fast enough for Twitter, it is definitely of interest to anyone working on significantly large and busy websites.
De gustibus et coloribus non est disputandum
who cares what twuufter is running off.
The more interesting aspect of all of this 'NoSQL' movement is how they believe that if they achieve some speed improvement against some relational databases, how that makes them so much better.
If you don't really need a database to run your 'website', then who cares if you use flat files or an in memory hashmap for all your data needs? Databases are not being replaced by NoSQL in projects that need databases. The projects that may not have ever needed databases may benefit by this NoSQL idea, but if you actually need a database... well, you better be really good at working around all kinds of problems that this will create for you.
I think that relational databases are good at what they do and that many projects may not need them, but if you do need them on the back end, you will end up with them on the back end. Of-course there maybe some caching/hashmaps/files on the front end but at the back stuff will be sorted out within a real datastore.
Is there really a huge issue with rdbms speeds? Well if there is something there, that's what needs to be looked at. If RDBMSs are not fast enough, that's just an opportunity to work more on them to speed them up.
You can't handle the truth.
Yes, because twitter is the epitome of robustness and speed. Oh wait... Just in the 2 months of this year alone they've had something like 4 outages.
Twitter's only moving to this new database written in Java because everyone else is.
Mod me down, my New Earth Global Warmingist friends!
I suppose then why would we care if any site made any random change to any part of its infrastructure?
Twitter is a -very- busy site.
They are changing their infrastructure to accomodate. Here's what they looked at, here is what they chose. If you are looking for something with equal performance, you don't have to shop around.
No way. Their architecture is about as "best guess" engineering as Facebook. I don't think that's actually what engineering is. "Maybe this one will work?"
In the meantime, I have not been able to update my avatar image on Twitter, and TwitPic-like feature is still a faint glimmer in Twitter's amateur eyes. Speaking of missed opportunities, why drive so much traffic to Twitter parasites Bit.ly, TwitPic, TinyURL, Twitition, TwitLonger?
What in the world are Twitter's engineers actually DOING should be the real question.
Kriston
I've never dealt with an EMP but a more realistic threat with similar effects would be planning for a hurricane or earthquake. I used to work at a international bank and we had to deal with both (offices in FL and CA). For the most part the best solution was to have an identical setup at another office and having all applications available via VPN and/or web access. We had a separate pipe that was used only for backup data transfers. The DB transaction logs were written both locally and remotely. All user files saved to the server were immediately copied to the backup server. On several occasions the systems were tested due to black/brownouts. The users were sent home where they could work just as effectively as the office.
Our general emergency plan for hurricanes (I worked at the FL office we used the CA office as our backup). Was to let the users go well in advance of the hurricane and switch CA to being our primary servers with FL as the backup. Once the users were settled then they could continue working from home. The only way we would be screwed is if a hurricane and earthquake happened simultaneously. At that point we'd have to restore VM backups on hardware located at the main corporate offices in NYC or Sydney.